The plantation system relied on slavery to be profitable. Because of this, slavery persisted as a legal institution, despite a growing sensibility that it was immoral and should be outlawed. Tensions over slavery led to the Civil War, which formally abolished slavery and the plantation system.
However, the plantation system as an ideal lingered on, its ideology affecting real history. In its ideal version, the planation system was predicated on an ideal of a natural hierarchy. Some groups of people were held to be innately superior to others. Men were superior to women, and whites were superior to blacks. Whites with the right bloodlines and ancestry were innately—genetically—meant to rule. If people simply accepted their rightful place in a pre-ordained system, life would run harmoniously, said general public opinion. This myth persisted into the twentieth century, carrying with it the myth of the happy, singing slave on the happy plantation. Nostalgia for this construct helped support state laws that lingered past the mid-twentieth century and were designed to keep blacks in a lower place in the social order.
The plantation system was significant in American history for at least two main reasons.
First, the plantation system came to define the culture and economy of the South. In that region, the plantations came to dominate the economy. This created an economy that had fewer small businesses and small farms than the North. It also created a society that was aristocratic. The Southern society was not very egalitarian. Instead, it was dominated by plantation owners who thought of themselves as the elite of society.
Second, the plantation system was, of course, based on slavery. The plantation owners needed people to work for them. The conditions in which the people were expected to work were too harsh to attract much in the way of free labor. Instead, the plantation owners used slaves.
These two factors helped very much to lead to the Civil War. The differences in the cultures and economies of the North and South helped to push the two sides apart. The tensions between the two regions eventually caused the Civil War.